
Glass. 
Book. 



Bulletin No. 19. Agros.47. 

U. S. DEPARTMENT OF AGRICULTURE. 

DIVISIOX OF AGEOSTOLOGY. 
[Oras^ ami Foragfe Plant f nvestigatioiiN.] 



The Structore of the Caryopsis of Grasses with reference 
TO their Morphology and Classification. 



BY 



P. BEVERIDGE KENNEDY, Ph. D. 



PREPARED UNDER THE DTRECTIOX OF F. LAMSOX-SCRIB^^ER. AGROSTOLOGIST. 




WASHmGTo:^r: 

GOVERNMENT PRINTING OFFICE. 
1899. 



/ 



JLLETIN No. 19. Agros.47. 

U. S. DEPARTMENT OF AGRICULTURE. 

DIVISION OF AGROSTOLOGY. 
[Orass and Forage Plant InvestigationN.] 



B^6 



fHE Structure 



OF THE CaRYOPSIS OF GRASSES WITH REFERENCE 

TO THEIR Morphology and Classification. 



p. BEVERIDGE KENNEDY, Ph. D. 



PREPARED UNDER THE DIRECTION OF F. LAMSON-SCRIBNER, AGKOSTOLOGIST. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE, 
1899. 



QV.A-'* ■" ;,6 



A-l^ 



jH^R 14 l9Cd 
D> ot D. 



^ 
^ 



LETTER OF TRANSMITTAL 



U. S. Department of AaRicuLTURE, 

Division of AanosTOLoaY, 
Washington, D. C, May 4, 1899. 
Sir : I have tlie honor to transmit herewith and recommend for pub- 
lication as Bulletin Xo. 19 of this Division the manuscript of a report 
on the structure of the caryopsis of grasses, ordinarily termed the grain 
or seed. This report, prepared by Mr. P. Beveridge Kennedy, by special 
authorization through the Agrostologist, contains much of histological 
interest, but is of special value on account of the important facts brought 
out in the investigations relative to the morphology and classification 
of grasses. Mr. Kennedy was formerly assistant chemist in Toronto 
University, Canada, and for the past three years has been studying at 
Cornell University, devoting special attention to the investigation of 
grasses. 

Kespectfully, 

F. Lamson-Scribner, 

Agrostologist. 
Hon. James Wilson, 

Secretary of Agriculture, 



INTRODUCTION. 

{___ 

The fruits and seeds of plants present characters which are less sub- 
ject to variation than any of the other organs or parts. In consequence, 
these characters are of the highest importance in studying the classifi- 
cation and relationships of j)lants. They are employed in separating 
the larger groups^ and in some cases ordinal characters are based upon 
them 5 and within many families the fruit affords the best diftbrential 
characters for the separation of subtribes, and even genera. To what 
extent the fruit, or caryopsis, of grasses maybe employed in determin- 
ing the relationships of the various tribes and genera is to some extent 
indicated in the following paper. Enough is presented to show that 
the characters possess great value in this connection and clearly empha- 
size the interest and importance of a knowledge of the structure and 
morphology of the caryopsis of the different tribes of Graminese — a 
subject here treated for tlie first time in the English language. 

The structure of the fruits of the cereals has been investigated to 
some extent at a number of the agricultural colleges and experiment 
stations, but the cultivated grains only represent three of the thirteen 
tribes of grasses. 

F. Lamson-Scribner. 

4 



CONTENTS 



Page. 

Historical review 7 

Summary 13 

General description of tlie fruit 13 

The scutellum 14 

The epiblast 15 

The plumule-sheath 19 

The root system 20 

Lateral buds : 20 

The fihro-vascular system 21 

Homology of the parts of the embryo 23 

Detailed descriptions of fruits 26 

Tribe Mayde?B 26 

Tribe Andropogonese 27 

Tribe Zoysieaj 28 

Tribe Tristegineae 28 

Tribe Panicese 28 

Tribe Oryzeee 29 

Tribe Phalarideaj 30 

Tribe Agrostidese 30 

Trib^ Aveneae 31 

Tribe Chloridese 32 

Tribe Festucei© 33 

Tribe Hordeee 33 

Tribe Bambuseaj 35 

Kelationship and systematic connection of the tribes 35 

Bibliography 38 

Explanation of lilates 42 

5 



ILLUSTRATIONS 



Page. 
Plates I-VIII. Structure of tlie Gary opsis of Grasses 44 

6 



THE STRUCTDRE OF THE FRUITS OF GRASSES WITH REFERENCE TO THEIR 
MORPHOLOGY AND CLASSIFICATION. 



HISTORICAL REVIE^AT. 

The first writer to mention the fruits of grasses from a morphologi- 
cal point of view was Malphigi/ who described the embryos of Triticum 
and Arena in 1687. He regarded the scutelkim as representing the 
cotyledon. Nothing further was written concerning the embryo of 
grasses for a hundred years, when Gaertner^ described it in 1788. He 
studied a considerable number of species, especially in regard to the 
scutellum. The name ''scutellum" was first used by him. He 
regarded the '^ vitellus " as a transition between the endosperm and 
the cotyledon. A. L. de Jussieu^ in describing the grass fruit used the 
term ''lobus'' implying the cotyledon. 

In the year 1808 Poiteau^ concluded that the sheath in the embryo, 
called " vitellus " and ^' scutellum " by Gaertner, is a true cotyledon. 
He decided that the epiblast must be the rudiment of a second cotyle- 
don, because of its position opposite to the cotyledon or scutellum. 
Richard^ in the same year i^resented the view that the scutellum 
originates from the lower i^art of the radicle, and that therefore the 
scutellum is a lateral protuberance of the radicle. By imagining 
the plumule raised in such a manner that it stands at right angles to 
the long axis of the scutellum, he constructed an homology with the 
embryos of the Xaitidacece, Alismacece, Hydrocliaridacece^ and Xymplia- 
cece. The word epiblast originated with Richard. He regarded it as 
a continuation of the root sheath, basing his opinion on a section cut 
obliquely through the embryo of Oryza. 

In 1809 Kirbel^ compared a number of embrj^os of the grasses in the 
resting and germinating stages with those of other monocotyledons. 
He believed that the scutellum represented a cotyledon and that the 
epiblast was a reduced cotyledon. In another work" Kirbel regarded 

* Opera omnia. 1687. 

2 De fructibus et seminibus plantarum. 1788. 

3 Genera plantarum secundum ordines naturales disposita. P. 28. 1789. 

^ Memoire snr I'embryon des Graminees, des Cyp^racees et du Xelumbo. 1808. 

5 Analyse des embryons Endorh. on. Monoc. et part de eel. d. Gr. 1808. 

^ Elements de Physiologie vegetable, r. I. 1809. 

' Examen de la division des v^getaux en Endorhizen et Exorbizes. 1810. 



the plumule- sheath as belonging to the cotyledon, but in 1815 returned 
to his former view. Treviranus ^ opposed Itichard's view and regarded 
the scutellum as a cotyledon. He speaks of the scutellum as enlarging 
itself the length of the seed and taking on a yellowish color, which is 
certainly not the case. Turi^in^ agreed with Mirbel that the embryo 
has two cotyledons. According to Cassini ^ the embryo of the grasses 
is composed of an axis, a cotyledon, one or two radicles, a plumule, and 
one or two '^ carnodes." His ^' cotyledon " is the plumule-sheath, while 
the "carnode," a name for the scutellum, he regards as a protuberance 
of the radicle. Kaspail^ compared the fruit and the flower. He 
believed that there was also an homology between the embryo and the 
culm. On examining the cotyledon he discovered a large nerve, join- 
ing the two nerves of the plumule-sheath at the base. From this he 
concluded that the scutellum is homologous to the peduncle of the 
aborted flower in the spikelet and to the sheath of the culm-leaf He 
compared the xflumule-sheath with the two-nerved palet in the spikelet 
and to the first leaf of the vegetative bud, and the endosperm to the 
flowering glumes of the spikelet and to bracts on the culm. 

Dr. G, A. Agardh^ in 1826 compared a longitudinal section of the 
embryo of Ruppia with the grass embryo and fruit, and found a great 
similarity between them. He regarded the entire endosperm of the 
grasses as the cotyledon, and the scutellum as a covering of the same. 
This, however, is impossible, as the scutellum never surrounds the 
endosperm. Bernhardi^ believed that a cotyledon must, aside from its 
function of nourishment, also act as a i)rotective organ to the young 
leaves. He therefore regarded the plumule- sheath as a cotyledonary- 
sheath and the scutellum as a cotyledon. Bischoff ^ also believed that 
the scutellum and epiblast are two cotyledons. He regarded the 
caryopsis as having an embryo with alternate cotyledons, without how- 
ever giving any special grounds for this opinion. M. J. Schleiden^ 
was the first to study the development of the grass embryo. Accord- 
ing to him the scutellum and the plumule- sheath together form the 
cotyledon. He regards the epiblast as an outgrowth of the cotyledon, 
since it is connected with the main axis lower down than the cotyledon 

1 Yon der Entwickelung des Embryo und seiner Umhiillungen im Pflanzen-Ei. 
1815. 

2 Memoire sur linfiorescence des Gramin(?es. Ann. d. Mus. d'bist. Nat. 1819. 
^L'analyse de I'embryon de Graminees, Jour, de Pbysique. T. 91. 1820. 

•* Sur la formation de I'embryon dans les Gramin^es. Ann. des Soc. Natur, Series 1, 
vol. 4, plates 13-14, 1824, 271-290. 1824. 

5 tjber die Eintbeilung der Pflanzen nacb dem Cotyledon und besonders iiber den 
Samen der Monocotyledonen. 1 Nov. Act. C. B. C, T. XIII, P. I. 1856. 

^Ueber der merkwurdigsten Yerscbiedenheiten des entwickelten Pflanzenembryo. 
Linnaea. 1832. 

'Lebrbucb der Botanikl. 1834. 

8 Einige Blicke auf die Entwickelungsgeschicbte des vegetale Organ bei den Pban._, 
Wieg. Arcbiv. Ill, I. 1837. 



itself. Atlrien cle Jussieu ^ differed from liis father in the interpreta- 
tion of the parts of -the embryo, believing that the scutelliim is not a 
true cotyledon but only a lateral appendage of the axis which resembles 
one. This view has been held by many up to the present time. Eegel - 
considered the plumule-sheath the true cotyledon and the scutellum 
first as a stipule and again later as a bract from which the plumule 
arises laterally. In the same year Reisseck^ advanced the opinion 
that the plumule-sheath is an axillary bud and that the cotyledon 
(Samenlappe) is an organ of the aborted terminal bud and the protect- 
ing leaf of the iilumule, and that the epiblast is united with the 
cotyledonary-sheath, which is evidently also a part of the cotyledon. 
Lestiboudois ' regarded the plumule-sheath as the cotyledon, but con- 
sidered the scutellum of no significance, because only the former is 
traversed by fibro vascular bundles, hence resembling two leaves grown 
together. 

Hofmeister^ interpreted the embryo in diff'erent ways, describing the 
development of Zea. He called the scutellum the cotyledon and the 
plumule- sheath a part of it. A few years later, in another work,^ he 
compared the so-called scutellum of the embryos of Zea ana Andropo- 
gon sorghum with the first leatless structures of Zoster a. Demoor " 
investigated a large number of the fruits of grasses in the mature 
stage, and also their development. He regarded the scutellum as the 
true cotyledon of the grasses, and the plumule-sheath not as represent- 
ing the ligule, but as a sheath of a i)rimordial leaf. This would not, 
however, correspond to the alternating arrangement of the leaves of 
grasses, a difficulty which he bridges over by citing that there is no 
opening of the sheath in Melica uniflora because of the gro wing- 
together of the two margins of the leaf. He admits, however, that he 
has not been able to observe this. J. 0. Agardh^ speaks of the embryo 
as sometimes presenting a thalloid form. Schacht^ considered the 
scutellum as the cotyledon, the plumule-sheath as the first leaf, and 
the epiblast a part of the cotyledon. 

Hofmeister,'° writing again concerning the grass embryo, stated: "I 
still regard the scutellum of the grasses and the analogous structure 

1 Sur les embryons monocotyledones. Compt. Rend, des Soc. de I'Acad. des Sci- 
ences, 9 : 15-31. 1839. 

2 Beobaclitungen iiber den Ursprung der Stipeln. Linnaea, 17. 1843. 

3 Monocotylisclier Embryo. Bot. Zeit. 1843. 

^ Phyllotaxie anatomique, Ann. des. sc. naturelles, ser. Ill, 10 : 15. 1848. 

^Die Entstehung des Embryo der Phauerogamen. 1849. 

^Ziir Entwickelungsgescbichtc des Zostera embryo. 1852. 

^Note sur Tembryon des Graminees. Bull, de I'Acad. roy. des Sci. de Brux, 1853. 

^Theoria system, plant. ^ 1858. 

9 Lelirbucli der Anatomie und Physiologie der Gewacbse. 2, 1859 und das Mikro- 
scope, 224. 1862. 

i^Neue Beitrage zur Kenntniss der Embryobildung der Phanerogaraen Abhand. 
d.er konigl. sachs. Gesellscbaft. d. Wieu. 1861. 



10 

of Zostera as an outgrowth from the axis, and not as a leaf." In this 
he agrees with Adr. de Jussieu. A. Gris,^ studying the embryo of Zea 
from a physiological standpoint, also regarded the cotyledon as a lat- 
eral expansion of the axis, modified iu such a manner as to become the 
principal absorbing organ of the embryo. 

Duchartre^ stated that the embryo is remarkable in having an oval, 
flat, or slightly curved, bud-like expansion at its base, called by Gaertner 
the '^ scutellum.^' Tbis organ directly adjoins the endosperm by its 
dorsal face. In front of it is another shoot, which Eichard calls the 
"blaste." Le Maout and Decaisne^ regarded the scutellum as a 
cotyledon, which is often split along its outer face, showing tlie rad- 
icle and i)lumule. The plumule is^conical and composed of one to four 
X^rimary convolute leaves. They regarded the plumule sheath as the 
first leaf of the plumule. Sandeen* investigated a large number of 
ripe embryos and concluded that the scutellum is a thallus formation 
and that the plumule is a protuberance of the axis. 

Sachs ^ regarded the scutellum as an outgrowth of the axis beneath 
the cotjdedon and the plumule-sheath as the cotyledon, enveloping the 
whole plumule like a mantle. Han stein ^ studied the development of 
Bracliyi)odmm from the embryo sac to its maturity. He regarded the 
scutellum as a leaf and a cotyledon, and both the plumule-sheath and 
the epiblast as trichomatic projections. This is difficult to imagine. 
Van Tieghem"^ reviewed the subject, illustrating the parts of the 
embryos of Trlticuyn cestivum, Hordeum vulgare, Avena sativa, Phalaris 
canariensiSj Zea mays, and Andropogon sorghum vulgare, briefly stating 
his own objections to the views previously held. He considered that 
the scutellum and plumule sheath together represent the cotyledon, 
which has at its opposite side a small protuberance called the lobule or 
epiblast. Owing to the presence of two vascular bundles in the 
plumule-sheath, he calls it a double stipule united at the margins, and 
homologizes the scutellum and plumule sheath with the leaf and ligule. 

Hegelmaier^ discussed the grass embryo from its developmental 
history, giving excellent figures of Triticum (estivum. He also noted 
the occurrence of secondary roots in Coix, Hordeum, Secale, Avena, 
Triticum, and other genera, concluding with Van Tieghem that the 

1 Recherches anatomiques et physioloques sur la germin. Ann. des Sci. natnrelles, 
ser. 5, 2 : 1864. 

2 Elements de Botanique. 1867. 

^ Recherches anatomiques et physioloques sur le germin. Ann. des Sci. naturelles^ 
ser. 5, 2 : 1864. 

^ Bidrag till kaenn ed omen om Grasembryots byggnad och Utweckling. Acta 
Uuivers, Lundens, 1868. 

sLehrbuch der Botanik, 474. 1868. Eng. Trans, and revision by S. H. Vines, 1882. 

^Die Entwickelung des Keimes der Monocot. and Dicot. Botanis, Abhand, 47. 
1870. Taf. 14, figs. 11-21; Taf. 15-18. 

'Sur les Cotyledons des Grarainees. Ann. des Sci. naturelles, series 5, 15 : 723-276. 
1872. 

*'Zur Entwickelungsgeschichte monocotylischer Keime, etc. Bot. Zeit. 1874. 



. 11 

scutellum and plumule- sheath together correspond to the cotyledon of 
the other monocotyledons. A. Stephen Wilson ^ held that the cotyle- 
don of the grasses had not yet been correctly interpreted, and that 
the morphological interpretation lay in whether the two vascular 
bundles of the plumule-sheath represent the middle nerves of two 
leaves or whether they only occur to strengthen the organ. In com- 
paring this with the. leaves in the terminal bud of the rhizome of 
Agropyron repens he found a difficulty, owing to the latter being many- 
nerved. He believed that the scutellum certainly has the function of 
a cotyledon and is a nourishing organ for the embryo at germination, 
but whether the plumule- sheath is also a nourishing organ is left in 
doubt. 

Gordon 2 studied the morphology of the inflorescence. He says that 
the node-like swelling at the base of the plumule-sheath occurs very 
generally in the grasses. It appears to be a part of the node, but in 
reality is only a circular swelling at the base of the closed sheatb. 
The proper node lies underneath this swelling. The plumule-sheath 
must exercise a certain pressure on the axis, and if axillary buds are 
l^^esent this pressure must have a certain influence on the plumule. 
The author speaks of the well-known organ, which denotes the origin 
of a branch, and which is looked upon by most morphologists as a two- 
keeled simple ''Yorblatt" (prophyllum), with its back turned toward 
the main axis. The axillary shoots in Zea, Tripsacum^ Coix, and mauy 
others make a cavity or groove in the culm, showing that they have 
developed under pressure of the sheath. The tissue at the base of the 
culm remains soft and capable of growth for a long time as a basal 
vegetation point, lu other grasses, such as Arundo and Fhalaris, the 
axillary shoot does not press itself into the culm. In these the grow- 
ing i3oint breaks through the sheath to the light. In Arundinaria the 
sheath soon dries up and the growing poiut has nothing to hinder it. 
Attempting an analogy between the fruit and the spikelet, he con- 
cluded that the plumule-sheath represents two leaves grown together. 
Certain Graminew, he says, have one or two buds in the axil of the 
plumule sheath, each with a prophyllum. 

Warming^ regards the scutellum as the cotyledon and the i^lumule- 
sheath as an independent leaf, the latter because an internode is occa- 
sionally found. Klebs"^ agrees with Van Tieghem. HackeP believes, 
as does Warming, that the epiblast is a rudimentary second cotyledon. 

' On the envelope of the plumule in the grass-embryo. Trans, and Proc. of the Bot. 
Soc. of Edinburgh. 13 : 457. 1879 (with plate). 

2 Etudes morphologiques sur la famille des Graminees. Revue des Sci. naturelles, 
Montpellier. 1879. 

^'Handbog i den Systematiske Botanik. Trans, by Potter. 1895. 

^ Beitrage zur Morphologie und Biologie der Keimung. Untersuch aus d. Bot. 
lustitut der Lubingen. 

^Echte Graser. Engler und Prantl. Pflanzenfamilien, 2 : 1887. 2. Eng. Trans, 
by Scribner and South worth. 1890. 



12 

Eegarding it as a cotyledon explains the peculiar position of the first 
leaf over the scutellnm. Many authors, he says, regard the plumule- 
sheath as a part of the cotyledon, surely an incorrect idea. Lermer 
and Holzner^ in an exhaustive histological treatise on Hordeum vulgare 
describe in detail the different parts of the fruit. They regard the 
scutellum as a shield-like expansion of the hypocotyl, acting as a 
special absorption organ, and the plumule as composed of four leaves 
inclosed in a plumule-sheath, but attempt no interpretation of the 
latter view. 

Bruns^ has investigated the grass embryo chiefly from a systematic 
point of view. He describes and figures a large number of genera of 
each of the tribes. He regards the scutellum as one cotyledon, and 
the epiblast as a second, much reduced on account of the great 
development of the former. He considers it of no consequence from a 
systematic standpoint whether or not the scutellum and the epiblast 
are regarded as two cotyledons, provided it is granted that they 
represent two leaves, as the cotyledons are the first two leaves placed 
together. The plumule sheath is the thickened first leaf of the plumule 
especially adapted for protecting the young leaves. It has no blade, a 
common characteristic of the lower leaves of grasses. Schlickum,^ in 
comparing the cotyledons of the monocotyledons, says that when the 
cotyledon has assimilating functions to perform its lamina displays a 
differentiation into a nutrient portion, the haustor, and a conducting 
portion, the conductor. In the grasses the conductor is very rudi- 
mentary or entirely supi^ressed, while the scutellum is transformed into 
the haustor, which bears no resemblance to a foliage leaf. The epiblast 
is probably an outgrowth of the coleorhiza. When the cotyledon does 
not emerge above the soil its function is to take up, by means of the 
haustor, the nutrient substances present in the endosperm, and to pro- 
tect the rudimentary leaves by the formation of a more or less 
developed cotyledonary sheath. 

Finally, Celakovsky^ reviews the work of previous investigators and 
criticises them especially in regard to the homology of the epiblast 
and plumnle-sheath. He believes that the true morjihological nature 
of the parts can only be determined by investigating along many dif- 
ferent lines, and if all these lines point toward the same conclusion, 
then surely it must be the correct one. The writer investigates the fruit 
according to the four following lines: (1) Ontogeny^ (2) taxonomy; 
(3) anatomy; and (4) progressive and retrogressive metamorphoses. 
He then attempts to find out where the scutellum and plumule-sheath 
are joined at the base; where they separate; and whether the plumule- 

iBeitrage zur Keantniss der Gerste. Miinchen, 1886. Extract by Brown and 
Morris Chem. Soc. Jour., vol. 57. 1890. 

2 Der Grasembryo. Flora, 76 : 1892. 

3 Morphologiscber und auatomischer Vergleich der Cotyledon nnd ersten Keim- 
blatter der Keimpflanzen der Monocotyledon. Bibl. botau. Heft. 35. 1896. 

^ Uber den Homologien der Grasembryo. Bot. Zeit., Sept. 1897. 



13 

sheath is inserted directly over the scutellum ; and, finally, how the 
insertion of the i)lumule-sheath becomes separated so far from the 
scutellum through the elongation of the axis. He also homologizes the 
grass fruit with Smilax, Fotamogeton, Ficus elastica, the mosses, and 
the leaf of the grasses. He regards the scutellum as the blade of the 
cotyledon, and as being homologous with the blade of the leaf. Over 
the scutellum is situated the plumule- sheath which is homologous to 
the ligule. The epiblast is the blade of an opposite second cotyledon. 

^ SUMMARY. 

The most important views of the different authors may be summed 
up as follows : 

1. The scutellum is the cotyledon; the epiblast a second independent 
leaf J the plumule-sheath a third leaf; while the first true leaf is the 
fourth lateral appendage of the embryo. — (Malphigi, Mirbel, and 
Poiteau.) 

2. The scutellum and the epiblast together form the cotyledon, the 
plumule sheath a second leaf, and the first true leaf becomes the third 
lateral appendage of the embryo. — (Schleiden, Shacht, and Decaisne.) 

3. The plumule-sheath represents the cotyledon, the scutellum and 
epiblast being only expansions of the axis or of the radicle; and the 
first true leaf then becomes the second lateral appendage of the 
embryo. — (Eichard, Adr. de Jussieu, Lestiboudois, Hofmeister, and 
Sachs.) 

4. The scutellum is the central portion of the cotyledon, the epiblast 
an opposite appendage of it, and the plumule-sheath an ascending i)art 
in the form of a protective organ ; the first true leaf then becomes the 
second lateral appendage of the embryo. — (Gaertner and Mirbel, at a 
certain time.) 

5. The scutellum and the plumule-sheath together represent the 
cotyledon, and correspond to the blade and ligule of the culm-leaf; the 
epiblast is a protuberance of the cotyledon on the opposite side. — (Van 
Tieghem and Klebs.) 

6. The sixth view is the same as the fifth, with the exception that 
the epiblast represents a second cotyledon opposite the scutellum. — 
(Celakovsky.) 

7. The scutellum is one cotyledon and the epiblast is the other, the 
plumule-sheath being the first leaf of the plumule.— (Bruns.) 

GENERAL DESCRIPTION OF THE FRUIT. 

The embryo of grasses stands isolated from those of other monocoty- 
ledons in possessing two peculiar structures, the ejnblast and plumule 
sheath. The following investigations were undertaken to determine 
the morphological significance and taxonomic value of these structures 
in the different tribes. Owing to the difficulties met with at the outset 



14 

in securing a suitable method, the work is not so complete as at first 
anticipated.^ 

The fruit of the Graminew was described first by Mirbel under the 
name "cerium" and rechristened later by Eichard '^caryopsis." 

Its contents at maturity consist largely of endosperm and embryo, 
the tissues of the nucellus, ovule, and ovary being almost completely 
displaced. The only remnants of the nucellus which are recognizable 
in the rij)e grain are the empty cells which spring from the funiculus, 
and the epidermis of the nucellus, which is continuous as a very attenu- 
ated layer of cells around both endosperm and embryo. Of the walls 
of the ovary only the inner one persists as a double layer of cells form- 
ing the testa or true coat of seed. Within the nucellus are one to four 
layers of cells with highly cuticularized walls. In section they are 
somewhat rectangular in form and constitute the gluten cells which 
contain the closely packed aleurone grains. 

Lying between the starch-containing portions of the endosperm and 
the embryo is a comparatively thick layer of compressed cells belong- 
ing to the scutellum. They are for the purpose of dissolving the starchy 
material of the endosi3erm during germination. The endosperm con- 
sists of tbin- walled cells packed closely with starch granules, embedded 
in a fine mass of proteid material. These starch containing cells each 
possess a nucleus which is not easily recognized. 

The embryo is situated laterally and at the base of the seed. It is 
diiiereutiated into the scutellum, the plumule, the radicle, and fre- 
quently the epiblast. The plumule is surrounded by the plumule-sheath, 
which sometimes has a slit-shaped opening on the side opposite to that 
of the scutellum. The plumule sheath is composed of a vegetation 
point and several layers of leaves. The radicle is inclosed in the lower 
part of the embryo, and at germination, before making its exit, must 
break through a protective mass of tissue, the coleorhiza, so called 
because it forms a kind of sheath around the radicle. Secondary radi- 
cles frequently occur in the mature and resting embryo. They arise in 
the axis usually just below the plumule. 

The vascular system may be traced down into the primary radicle, 
and also into the scutellum, plumule-sheath, and plumule. 

THE SCUTELLUM. 

The name ''scutellum" has been given to the cotyledon of the grasses 
because of its resemblance to a little shield. It has for its object the 
protection of the plumule and the absorption of nutrient materials from 
the endosperm. 

1 The author wishes to express his thanks to Prof. W. W. Rowlee for many helpful 
suggestions during the progress of the work; also to Profs. F. Larason-Scribner and 
W. J. Beal for much valuable material, and to Prof. F. C. Harrison, of the Ontario 
Agricultural College, at Guelph, Canada, and to Messrs H. R. Carveth and O. Shautz 
for aid in the discovery of a method. 



15 

Observing a cross section of any embryo, one sees that the scutellum 
surrounds the plumule like a sheath. In Zea (figs. 4 A-F, PL I), 
Andropogon (figs. 10 A and B, PI. 11), and others the plumule is almost 
completely surrounded by the scutellum, so that only a narrow oi:)ening 
may be seen. A longitudinal section oi Andropogon saccharatus (fig. 9, 
PI. II) shows the scutellum so completely surrounding the plumule that 
it appears as if an epiblast was present. By observing a cross section, 
however, it is seen that the margins of the scutellum surround the 
plumule with the exception of a small slit (fig. 10 B, PL II). At a point 
toward the ai)ex of the plumule sheath the scutellum bears a protuber- 
ance which projects over the plumule. This is especially distinct in 
Lygeum (fig. 25, PL lY), LoUiim (fig. 75, PL YIII), and Ammophila (fig. 
42, PL V). This part has been called the cotyledonary sheath (c. s.) to 
distinguish it from the plumule-sheath (x)l. sh.). 

At the base of the scutellum there is another protuberance in many 
embryos, such as Avena (fig. 44, PL Y), Triticum (fig. 69, PL YII), 
Anthoxanthum (fig. 29, PL lY), Uniola (fig. 61, PL YII), BuMlis (fig. 
58, PL YI), and Bechnannia (fig. 60, PL YI). Sometimes a deep cleft 
occurs, appearing as a separation of the radicle. In some embryos the 
scutellum has a distinct sheath and a blade. A striking example of 
this may be seen in Avena (fig. 44, PL Y), Spartina (fig. 53, PL YI), and 
Zlzania (fig. 22, PL III). 

The attachment of the scutellum to the axis varies considerably in 
different embryos. Desmazeria (fig. 63, PL YII) and Anilioxanthum 
odoratum (fig. 29, PL lY) have the attachment directly at the base 
of the plumule. In others there is a lengthening of the axis with the 
attachment at the base, leaving a very small proportion of the embryo 
to represent the hypocotyl: Zlzania (fig. 22, PL III), Homalocenchrus 
(fig. 28, PL lY), and Spartina gracilis (fig. 53, PL YI). 

The scutellum has at every i)oint where it comes in contact with the 
endosperm a layer of peculiar oblong cells called the epithelial layer. 
Sachs regards it as corresponding to the somewhat similar layer found 
in the cotyledons of the palms, and to the young epidermis of Eicinns 
and many other seeds. The scutellum, therefore, may be regarded as 
part of the cotyledon. 

THE EPIBLAST. 

The peculiar organ, the epiblast of Kichard, situated opposite to the 
scutellum, is not very well understood. Its occurrence in the Graminew 
is of much greater frequency than is generally supposed. Warming^ 
describes the fruit of the grasses, but does not mention the epiblast. 
He figures a fruit of Avena sativa, but does not represent the epiblast, 
which is always present and quite distinct. Yan Tieghem^ speaks of 
the existence of a second cotyledon in a dozen or less of the genera of 

1 Warming and Potter. 1895. 

-Comptes Rendus heb. Lean. I'Acad. des Sci. 124 : 1896 and 1897. 



16 

the Graminew. Unlike tlie scutellum, the epiblast has no vascular 
system, and on this account much dispute has arisen over its morpho- 
logical nature. This, however, is no proof against its leaf nature, as 
there occur many instances of reduced organs without fibrovascular 
systems. 

Although the e])iblast is usually very small in comi)arisoii with the 
scutellum, yet there are many grasses in which it reaches a considerable 
size. Zizania aquaUca (fig. 22, PI. Ill) has a well-marked epiblast 
extending from the base of the lengthened axis to about the middle of 
the plumule, or even further. 

In the genus Stipa there are marked differences in the size of the 
epiblast in the different species. 8. tenacissima (fig. 30, PI. IV) has a 
very small one; in 8. pennata it is long and attenuated; while in 8. 
richardsoni (fig. 36, PI. Y) and 8. viridula (figs. 32 and 33, PI. IV) it is 
very large and broad. Sometimes the margin of the epiblast is curved 
or deeply keeled, although in the large majority it is straight. Homa- 
locenchrus oryzoides (fig. 28, PI. IV) has a very large epiblast which 
greatly resembles the form of the scutellum. It is large and broad at 
the base and has a shield-like appearance. A small protuberance 
occurs at the base similar to that in the scutellum. 

A fact which seems to indicate that the epiblast has the same mor- 
phological value as the scutellum is, that it is inserted on the axis 
almost at the same height. Even in Zizania (fig. 22, PI. Ill), where the 
axis elongates to a great length and the insertion of the scutellum is 
almost at the base of the embryo, the epiblast is inserted directly 
opposite. 

The absence or i^resence of the epiblast appears to be fairly constant 
in the different tribes, and the presence of an epiblast in a tribe where 
the majority of the genera have none may indicate that it is not in its 
natural position. The tribes Andropogonew and Maydece, to conclude 
from the genera examined, might be regarded as being without an 
epiblast. The scutellum almost entirely surrounds the embryo, as may 
be observed in any of the cross sections figured, more especially among 
the Maydew. In the tribe Zoysiece there occur genera without an 
epiblast, as Nazia, Trachys, and Anthephora^ while Zoysia has a dis- 
tinct one. The THsteglnea'^ to conclude from Beckera and ArundineUa, 
have no epiblasts. The Panicece appear to be without an epiblast, tix^. 
only exception being Olyra^ which has a very large epiblast covering 
the plumule. From its great resemblance to the embryos of Leersia 
and Oryza it seems probable that it should be placed with them, or 
should form a separate intermediate tribe. The Oryzew appear to have 
a very large epiblast. The PhalarideWj so far as examined, vary, 
Antlioxanthum and Phalaris having small epiblasts, while Ehrliarta 
has none. 

ThQ AgrostidecB examined, although varying greatly in their external 
form, all possess an epiblast. In the large majority it is small, but in 



17 

some, as in Stipa, it is remarkably large, extending the wliole length 
of the plumule. The Avenece also, so far as examined, all possess an 
epiblast. It is in the Chloridece that the most remarkable and varying 
formations of the embryo are to be found. Eleusine (fig. 52 A-D, PI. 
YI) has a round nut-like fruit, with a small embryo having a very large 
epiblast; while i^partina (fig. 53, PI. YI) has a long fruit, with the 
embryo extending almost the length of the seed, but with no trace of 
an epiblast. Between these occur the genera BulMlis (fig. 58, PI. YI), 
Leptochloa (fig. 56, PI. YI), Astrehla (fig. oo, PI. YI), Cynodon (fig. 57, 
PI. YI), and Bechnannia (fig. 60, PI. YI), each with an epiblast. 

In the FestucecCj a very large percentage of the genera have a well- 
formed epiblast, but in Bromus and some others it is absent. Among 
the Eordecv, Secede (fig. 67, PI. YII) and Hordeum (fig. 35, PI. lY) are 
without an epiblast, while in Lolium (fig. 70, PI. YIII) and Triticum 
(fig. 69, PI. YII) it is present. Ulymus (fig. 72, PI. YIII) has a very 
light projection at the point where the epiblast is usually situated, and 
might be regarded as a transition stage between those with and those 
without an epiblast. 

Among the Bambusece only the genera Arundinaria (figs. 74, 75, 76, 
PI. YIII) and Bamhusa have been examined. They possess very large 
broad epiblasts. 

It appears, therefore, in most cases that the tribes Maydece, Andro- 
pogonece, Zoysiecej Tristeginece^ and Panicece are without epiblasts, while 
in the Oryzecv, Phalaridece, Avenece, Chloridece, Rordece, Festucece, and 
perhaj)s, the Bamhiisece, it is usually present. 

The bllowing table will show that it is not correct to regard the 
epiblast as usually wanting in the Gramineae. 



With ejjiblast. 







MATDE^. 


Without 


epiblast. 






Euchlaena. 

Zea. 

Coix. 

Tripsacum. 




^ 








ANDKOPOGONE^. 


*Saccharum.i 
Andropogon. 




1 

1 

* SORGHUM. 


*Eriantlius. 
Apluda 




ZOYSIE^. 


Perotis. 
* Trachys. 
Anthephora. 






Zoysia. 
Nazia. 



The genera starred (*) are taken from Bruus's work, not examined by the writer. 
20946— No. 19 2 



RISTEGINE.E. 



Aruudinella. 
Beckera. 



PANICE.E. 



Paspalum. 

PeLmisetom. 

Chsetochloa. 

"Panicum. 

Tricholsena. 

* Peniiisetum. 

*Berchtoldia (Chaetium). 

Cenchrus. 



ORYZE^. 



Oryza. 

Zizaiiia. 

Homalocenclirus, 

Lygeum, 

Pharus.^ 



PHALARIDE.E 



Ebrliarta. 



Phalaris. 
Antlioxautlium. 

Savastaua. 



AGROSTIDE.E. 



Stipa. 

Phleum. 

*Polypogon. 

Sporobolus. 

*Piptatherum. 

Calamagrostis. 

Eriocoma. 

Oryzopsis. 

Bracbyelytrum. 

Ammophila. 

Milium. 

Ch^turus. 

* Apera. 
Lagurus. 

* Aristida. 
Ciuna. 



Avena. 

Arrhenatheriim. 

Dautbonia. 

Aira. 

Holcus. 



Van Tiegbem. Ann. Sci. nat. Ser. 5, 15 : 240. 



19 



Spartina. 



Secale. 

Hordeum. 

Asperella. 



*Boissiera. 
* Schismus. 
Bromus. 
Gyuerium. 



CHLOKIDE.E. 




Leptochloa. 




Eleusine. 




Chloris. 




Beckmaunia. 




Cynodon. 




Astrebla. 




Biilbilis. 


HORDE JE. 




* Nardus. 




Loliuni. 




Triticum. 




*Aegilops. 




*Lep turns. 




Elymus. 


FESTUCACE.E. 




* Echinaria. 




Cynosurus. 




Festuca. 




Leptochloa, 




Melica. 




Koeleria . 




Korycarpus. 




Desmazeria. 




Dactylis. 




Poa. 




Panicularia. 




"" Lamarkia. 




* Avellinia. 




Briza. 




* Brachyi3odium 




Triodia. 


BAMBUSE^. 


1 Arundiuaria. 




" Bambusa. 



THE PLUMULE-SHEATH. 

This peculiar structure is found in all grasses, completely surround- 
ing and protecting the plumule, with the exception of a small opening 
or slit toward the apex on the side opposite to the scutellum. At ger- 
mination the young leaves break through this sheath, which soon 
afterwards dies down. The plumule- sheath always has two distinct 
vascular bundles situated laterally and slightly inclined toward the 
scutellum. Considerable controversy has arisen as to whether this 
organ is a part of the cotyledon or whether it represents the first true 
leaf of the embryo. This will be treated of later under the chapter on 
the homology of the parts. It usually originates directly under the 
plumule and close to the insertion of the scutellum, although it is 



20 

widely separated from the scutellum in many grasses. See Zizania and 
Homalocencliriis (figs. 22 and 28, Pis. Ill and lY). Because of its thick- 
ness, it is specially adapted for a protective organ. 

THE ROOT SYSTEM. 

The large majority of the embryos of grasses have only one radicle, 
situated at the base of the embryo, usually in a vertical position, but 
sometimes turned obliquely, as in Oryzopsis (fig. 38A, PI. Y) and Stipa 
richardsonii (fig. 36, PI. Y), or, again, comjjletely horizontal, as in 
Eriocoma (fig. 34, PI. lY), Oryza sativa (fig. 27, PI. TV), and Eleusine 
(fig. 52A-D, PI. YI). In Homalocenchrus oryzoides (fig. 28, PI. lY) it 
has a slightly upward tendency. 

There are, however, embryos with numerous lateral roots. Triticum 
cestivum (fig. 69, PI. YII) has four lateral roots, two on each side of the 
scutellum. Zizania (fig. 240-Q, PI. Ill) has three, situated directly 
under the plumule, a long distance from the main radicle. Coix (fig. 1, 
PI. I) has four radicles, obliquely one above the other on the axis. In 
the illustration only three are seen, as they are not all in the same i^lane. 
Sordewn vulgare (figs. 65, QQ, G and H, PI. YII) has eight secondary 
radicles, three on each side of the scutellum and two in front. On 
germination the i)rimary radicle is soon outstripped in growth by the 
secondary ones. Both the primary and secondary ones are surrounded 
by a compact mass of cells which form the coleorhiza or root-sheath. 

Each radicle terminates in a rootcap, the cells of which appear as 
regular continuations of the rows of cells in the radicle. The rootcap 
can thus be distinguished from the coleorhiza, in which the cells are 
very irregular. The rootcap is not connected with the coleorhiza. The 
former is produced from the embryonic tissue, while the latter is derived 
from the ijreembryonic tissue and is connected with the lower part of 
the scutellum. In dissecting out the embryo the radicle or radicles, 
with their rootcaps, easily separate from the coleorhiza, leaving the 
latter at the base of the sockets in the lower part of the scutellum. 

LATERAL BUDS. 

In a number of genera of the tribe Rordew there is a lateral bud in 
the axil of the plumule-sheath : Hordeum (fig. 65, PI. YII), Triticum (fig. 
69, PI. YII), Elymus (fig. 72, PI. YIII), and Secale (fig. 67, PI. YII). 
Bruns regards this as proving that the plumule-sheath must represent 
a leaf. Similar buds, however, may be found in Polygonum, Eumex, 
and a large number of plants with axillary stipules. Yan Tieghem 
describes and figures lateral buds in Avena sativa^ but it was not pos- 
sible, after making many paraffin sections through different embryos, to 
discover them. This circumstance is remarkable in that Avena belongs 
to the tribe Avenece, while all other genera in which lateral buds have 
been found belong to the tribe Hordece. Bruns, however, figures aud 
describes a Bamhusa with a large lateral bud in the axil of the plumule- 
sheath. 



21 

THE PIBRO-VASCULAR SYSTEM. 

The fibro-vascular system of tlie embryos of the Graminece ma}" be 
considered under three main divisions, according to the manner and 
place of insertion of the plumule-sheath on the axis and its connection 
with the scutellum. 

1. The plumule-sheath is inserted on the axis directly above the 
insertion of the scutellum: Sti:pa (fig. 36, PL V)^ Fhleum (fig. 41, PI. V), 
AmmopMla (Fig. 42, PL Y), and perhaps all of the Agrostidece. 

An example of this modification occurs in Stijm viridida (figs. 32 and 
33, PL IT). A vascular bundle passes through the entire length of 
the scutellum. At the insertion of this bundle on the axis two branches 
are sent ofi' from it which traverse the plumule-sheath (fig. 33, PL IV), 
while the main branch continues into the axis and then descends to the 
radicle. A little above this insertion numerous small bundles form and 
run uj) into the young leaves and vegetation point. As these different 
bundles are not all in the same i)lane, it is not i30ssible to obtain a sin- 
gle section showing them. In any transverse section of the j)lumule, 
however, the bundles of the plumule-sheath may be seen quite dis- 
tinctly. 

In Eriocoma cusindata (fig. 34, PL lY) the bundles ascend from the 
axis into the plumule-sheath, while in a cross section of Stipa ricliard- 
soni (fig. 37B, PL Y), taken below the insertion of the scutellum on the 
axis, the vascular bundle may be seen entering the radicle. Again, in 
Triticum (fig. 69, PL YII) a bundle may be seen entering the first true 
leaf. Hordeum (fig. 65, PL YII) shows the bundles passing up Into the 
second true leaf and the vegetation point, while several may be seen 
branching oft' from the axis into the secondary radicles. All the genera 
of the tribes Agrostidece and Sordece, so far as examined, have this 
arrangement of their vascular systems. 

2. The plumule-sheath is inserted on the axis at some distance from 
that of the scutellum, with which it is connected by a vascular bundle 
traversing the axis: Zizania (fig. 22, PL III) and Homalocenclirus (fig. 
28, PL lY). The embryo of Zizania aquatica (figs. 22, 23 A and B, 24 
A-T, PL III) has a remarkably long axis, which separates the insertion 
of the plumule-sheath and the scutellum to a very considerable degree. 
It will be noticed in the longitudinal section (fig. 22, PL III) that two 
vascular bundles traverse the axis, one terminating in the main radicle, 
while the other curves sharply round and traverses the long linear 
scutellum. The exceedingly large epiblast is devoid of any vascular 
system. In the transverse sections (fig. 24 A-T, PL III) it is found that 
in A, a section taken through the apex of the plumule-sheath, the two 
bundles have joined into one. In B they are beginning to separate, 
while in and D they are entirely free. Figure E shows a section 
through the tip of the first leaf of the plumule, the i)lumule- sheath with 
its two widely separated lateral bundles surrounding it. Figures F-L 
illustrate sections taken through the plumule at different heights, show- 
ing the arrangement of the leaves with their bundles. The bundle in 



22 

the center of the leaf is always a little larger than the lateral ones. 
The bundle of the scutellum now appears distinctly in all sections 
taken through the region of the i)lamule. N represents a section taken 
directly underneath the plumule-sheath. The bundles of the sheath 
have united with those of the leaves and ai^pear very irregular, with a 
secondary radicle appearing on each side. A little lower down a third 
secondary radicle is seen on the side of the axis next to the scutellum. 
The axis now for a considerable distance presents the appearance shown 
in P and Q, with two distinct, separate, vascular bundles in the center. 
At the base of the long axis one of these bundles situated nearest to 
the scutellum joins with the bundle of the latter, as in S, while the 
other continues down into the main radicle, as in T. This seems to 
prove conclusively that the plumule sheath is not an independent leaf, 
but that it belongs to the scutellum. 

There is no difference between this group and the first, represented 
by the Agrostidece^ except that between the insertion of the plumule- 
sheath and the scutellum there occurs a very loug axis representing 
the first node. 

3. The plumule- sheath is inserted on the axis at the base of the plu- 
mule, but its fibro-vascular bundles are not directly connected with 
that of the scutellum: Zea, Coix, Fennisetum, Faspalum^ Panictnn, and 
Spartina. Zea mays may be taken as typical of this arrangement of 
the vascular system, as shown by a series of sections from the radicle 
to the i)lumule (figs. 3, and 4 A-F, PI. I). Fig. 4 A represents a cross 
section through the main, radicle. There are two systems of vessels, 
consisting of six large ones toward the center and about sixteen smaller 
ones on the outside, which, along with their conjunctive tissue, make 
up the central cylinder. Section B, taken somewhat higher up, above 
the region of coleorhiza shows the axis with its bundles beginning to 
form round the i^eriphery of the central cylinder, the two systems of 
vessels remaining the same as in the radicle. The dark portions of the 
scutellum are sections through the lateral branches of the scutellum 
bundle. These peripheral bundles widen and come closer and closer 
to the center until they reach the condition figured in C, where there 
is an irregular mass of vascular strands and bundles Avith only a few 
of the vessels. Immediately above this the bundles arrange them- 
selves round the periphery, leaving only a few in the center, while a 
vascular strand branches off and penetrates through the cortical 
parenchyma into the scutellum, where it divides into an ascending and 
descending branch, as in D. The large vessels have returned to their 
original position, while the smaller ones have become fewer, and are 
arranged irregularly nearer the center. At E, a section taken through 
the upper part of the scutellum, two radicles emerge from the axis to 
the right. Vascular bundles are found both in the periphery and in 
the center of the cylinder. Tlie axis now continues in a regular form 
with its two systems of vessels and bundles arranged in the perix)hery, 



23 

until just below the plumule, where several bundles in the periphery 
unite on either side and branch off into the plumule-sheath. Soon 
numerous, bundles form in the center, until the whole axis is completely 
filled with them. These arrange themselves in a definite manner and 
run up into the leaves of the plumule. 

There is no direct connection between the vascular bundle of the 
scutellum and those of the plumule-sheath, both originating from the 
peripheral bundles of the axis separately. The same condition occurs 
in all the genera of the Maydece, Chloridece^ Fanicece, and Andropogo- 
nece examined, with slight modifications as to the number and size of 
the vessels and bundles. This would seem to indicate that these tribes 
are closely related to one another, although it is not exactly in accord- 
ance with Hackel's classification of the tribes with reference to the 
Chloridew. 

HOMOLOGY OF THE PARTS OF THE EMBRYO. 

To what do the scutellum, epiblast, and plumule-sheath correspond; 
from what have they been developed; and to what parts of the leaf and 
spikelet of the grasses are they homologous! 

The scutellum is at present generally regarded as the cotyledon, cor- 
responding to the single cotyledon characteristic of the grou}) of 
monocotyledons, but diflering from them in not emerging from the 
caryopsis at germination. 

The epiblast has been regarded in various ways by different authors. 
Bernhardi, Schleiden, Schacht, and, later, Van Tieghem, regard the 
epiblast as part of the cotyledon. Hanstein concludes that it is merely 
an insignificant trichomatic projection of the hypocotyl. The majority 
of writers, however, with Poiteau, Mirbel, and Bruns, regard it as a 
second rudimentary cotyledon, and in embryos in which it is wanting, 
look upon it as having become completely aborted. 

Van Tieghem Mn his new classification of the phanerogams based 
upon the ovule, revised his opinion concerning the epiblast, regarding 
it as a second rudimentary cotyledon, and explaining its partial or 
complete abortion as due to the pressure more or less exerted by the 
seed coat or pericarp upon the embryo. From this and other char- 
acters of the integuments and ovules he is led to believe that the 
Graminece are in reality dicotyledons, which have accidentally become 
monocotyledons. 

In spite of the fact that there has never been found the slightest 
trace of a vascular system in the epiblast, yet it seems most reasonable 
to regard it as a second rudimentary cotyledon. One inclines to this 
view from the study of the perfectly developed epiblasts of Romalocen- 
clirus, Zizania, and Oryza, where they are inserted on the axis opposite 
the insertion of the scutellum. 

' Comptes Rendus seanc. Tacacl. des Sciences, 124 : 1896-97. 



24 

The plumule- sheath is, of all the organs of the embryo, the most 
striking and difficult to explain. Three very different theories are 
held regarding its interpretation. To the first we attach the names of 
Hofmeister and Sachs, who regard it as an outgrowth of the so-called 
hypocotyledonary internode. 

The adherents of the second view regard it as an independent leaf 
belonging to the plumule and next in leaf arrangement to the scutel- 
lum. According to this the plumule-sheath, which is directly above 
the scutellum on the same side of the axis, would not correspond to the 
distichous arrangement of grass leaves: but if one regards the ei)iblast 
as a leaf, i. e., a second cotyledon, then the apparent disagreement is 
explained and the plumule sheath becomes the third leaf alternating 
with the epiblast. Bruns, who is a strong advocate of this view, sees 
no reason why Hanstein should deny the independent nature of the 
plumule- sheath because of its origin. 

Let us briefly follow the devolopment of Bracliypodium according to 
Hanstein's investigations. The young embryo is at first a spherical 
mass composed of three with sometimes a fourth smaller cell. These 
cells divide several times in all directions and the embryo takes on a 
club-shaped form, becoming longer and narrower at the base. This 
many-celled body is at this time without distinct internal or external 
differentiation. The lower-most cell, which has now become considera- 
bly divided, later goes to form the suspensor, while the two upper cells 
form the embryo jiroper. Soon the internal differentiation of the 
radicle can be seen with its dermatogen, peiiblem, and ])lerome. The 
second stage of development takes place iu the external part of the 
embryo. In the wall there occurs a depression which marks the divi- 
sion of the scutellum from the hyi)ocotyledonary part. The tissue 
immediately above this depression is the cotyledon, from which a part 
of the plumule-sheath soon emerges, while that on the lower side forms 
the vegetation point with its later-developed leaves. Tbe projection on 
the upper part of the embryo, i. e., on the upper side of the depression, 
shows again on its upper surface another depression similar to the first, 
thus forming a second projection. At the same time a projection in the 
form of a half collar has formed on the lower part below the vegetation 
point. These two projections stand opposite one another like lips. 
Finally they grow and their margins unite to form a complete cap over 
the x)lumule. The occurrence of a slit in the mature plumule-sheath is 
in all probability caused by the incomplete junction of the margins of 
these collar-shaped projections. The tissue above this second depres- 
sion, which sometimes curves down to a considerable degree pro- 
tecting the plumule, forms that part of the cotyledon known as the 
cotyledonary-sheath. Thus the origin of the plumule sheath indicates 
that it must be a part of the scutellum. To regard the plumule-sheath 
as an independent leaf as Bruns has done, one must look upon it as 
arising from a stem and not from a primordial leaf, which, according to 
Hanstein's investigations, is evidently the case. 



25 

The third view is that the plumule- sheath is a ligule like growth pro- 
ceeding from the scutellum as an inseparable part. The existence of 
an intermediate part between the insertion of the plumule-.sheath and 
that of the scutellum in many embryos, is relied upon by Bernhardi, 
Bruns and others as positive proof that there can be no connection 
between these organs. By many authors it has been called an inter- 
node, which latter always develops between two leaves and not between 
two parts of a leaf. 

Bruns says that while in Euchlcena tbe two insertion points are near 
together, it hardly seems plausible in the case of Spar Una ^ and espe- 
cially of Zizaniaj to regard two organs which are so widely separated 
from one another as the same. The occurrence of a bud in the axil of 
the pUimule-sheath also influences his conclusion that the plumule- 
sheath must represent a leaf. 

From a careful study of the vascular system of tbe different tribes, 
together with Hanstein's investigations, one is led to believe with Van 
Tiegliem and Celakovsky that the so-called internode between the 
plumule-sheath and the scutellum, occurring so distinctly in Zizania 
and EomaloceuchruSj and not at all in the genera of the Agrostidece, 
is nothing but the first unusually lengthened node. The ligule-like 
growth, the plumule-sheatb, is usually inserted directly over the scutel- 
lum and the plumule-sheath in the mature fruits of Zizania, Homalo- 
ceuchruSy and the Chloridecv, or as in Oryza (according to Bruns and 
Schlickum) soon after germination. 

The vegetative leaf of the grasses is composed of a sheath and 
blade and a more or less strongly developed ligule inserted at the 
point of junction of the sheath and blade. The ligule is usually small, 
without chlorophyll and stomata, and exclusively parenchymatous, 
but as Duval-Jouve^ has shown in Ammopliila arenaria, it attains a 
length of about 4 centimeters and possesses nerves with cliloroi)hyll 
and stomata. The ligule thus represents a double sheathing axillary 
stipule. 

Of the three i:)arts of the leaf it is the sheath which develops last, 
by an intercalary growth, which raises up the blade and ligule. 

Comparing the culm leaf with the scutellum and plumule-sheath, the 
cotyledonary leaf of the embryo, one finds that the latter has no 
sheath. Its sessile blade, however, elongates to form the scutellum, 
while the pumule-sheath, which is homologous with the ligule, attains 
a great size with vascular bundles similar to the ligule of Ammopliila 
arenaria. It is provided with two prominent lateral nerves, which 
later acquire chlorophyll and stomata. 

The homology of the parts may in the same manner be carried out in 
the spikelet. The awn of the floral glume, when present, is regarded 
as corresponding to the blade of the leaf, and therefore to the scutel- 
lum of the embryo. When the awn is inserted on the back of the 

1 Anatomie de Tarete des Graminees Mem. de I'ac. des Sci. et lettres. Montpellier. 
1871. 



26 

glume some distance from tlie apex, that part between the insertion 
and the apex is regarded as corresponding to the ligule, and, in conse- 
quence, to the plnmule-slieath. That part of the glume below the 
insertion of the awn is regarded as the sheath of the leaf, while its 
analogous structure in the embryo has been arrested in its development. 
Colomb,^ who has investigated the stipules of many i^lants, also takes 
up the ligule and sees in it an analogy to the stipules of Potamogeton 
and /Smilax. Oelakovsky ^ makes a comparison between these, adding 
another plant, Ficus elastica. He carries his homology still further to 
the mosses, believing that the moss capsule is homologous to the 
cotyledon and the seta or their bases to the hypocotyl. 

DETAILED DESCRIPTIONS OF FRUITS. 

Tribe Mayde^. 

The fruits of the genera of this tribe are large, ellipsoidal or round- 
ish, and inclosed, with the exception of Zea, in a hard capsule formed 
of the glumes or of part of the articulate rachis. They have a very 
large embryo, with the scutellum almost completely surrounding the 
plumule. 

Coix lachrymw-joM L. (figs. 1, 2 A-G, PI. I). The structure of the 
embryo of Coix resembles that of Zea mays^ the main difference con- 
sisting in the former possessing four lateral radicles. Only three are 
shown in fig. 1, the fourth and uppermost one not being in the same 
plane. Fig. 2 A represents a transverse section through the upper 
part of the plumule, showing the plumule- sheath with its two bundles 
and the first and second true leaves in their normal position. A sec- 
tion through the base of the plumule (fig. 2 B) shows the plumule- 
sheath and a small part of the first, true leaf. Within is the axis with 
its numerous bundles which belong to the leaves of the plumule. 

At is the axis, with its numerous bundles and the i)lumule-sheath. 
Some of the bundles in the periphery of the central cylinder unite and 
branch off into the plumule- sheath on each side. A little lower down, 
between the insertion of the plumule sheath and that of the scutellum 
the axis appears with its numerous bundles arranged in the periphery 
of the central cylinder (fig. 2 D). Fig. 2 E shows the scutellum 
inserted on the axis by its broad, fibro vascular bundle, at the same 
time cutting through the first lateral radicle on the opposite side. A 
number of ducts are scattered here and there in the axis. The axis 
terminates in the lowermost radicle, the central cylinder having six 
distinct ducts or vessels. Fig. 2 F shows a section through the upper 
part of the lowermost radicle and one of the lateral radicles, while G 
represents a section through the lowermost radicle. Each radicle is 
provided with a root-cap while the coleorhiza surrounds them all. The 

^ Recherclies sur les stipules. Ann. des Sci. nat. Ser. 6, 1 : 19. 1887. 
2 Ueber die Houiologien des Grasembryo. Bot. Zeit., Sept., 1897. 



27 

scutellum entirely surrounds the remainder of the embryo, as may be 
seen in cross section or in the longitudinal section (fig. 1). There does 
not appear to be such a direct connection between the vascular bundle 
of the scutellum and those of the plumule-sheath, as in Zizania (fig. 22, 
PI. Ill), Eomalocenchrus (fig. 28, PI. lY), and other embryos. The vas- 
cular bundle of the scutellum, as in the other genera of the Maydece^ 
branches into two, one traversing the upper and the other the lower 
13art of the scutellum, and these again sending off lateral branches. 
The leaves of the plumule are arranged as in all grass embryos. 

Zea mays L. (figs. 3, 4 A-F, PI. I). — The vascular system of Zea has 
already been described. The general structure of the embryo differs 
but little from that of Goix, Instead of four large lateral radicles it 
has one large main radicle (fig. 4 A) and two smaller secondary ones at 
the insertion of the scutellum bundle on the axis. The scutellum sur- 
rounds the remainder of the embryo like a mantle, the margins almost 
coming together, but separated by a long, narrow groove (figs. D and 
E). There is a. deep cleft between the base of the scutellum and the 
coleorhiza (fig. 3). 

Tripsacum dactyloides L. (figs. 5, 6, 7, A-B, PI. I). — The embryo of 
Tripsacum is very similar to that of Zea and Coix, except that it has 
only one radicle. The axis is remarkably long and consists of a num- 
ber of vascular bundles, as in Coix. About halfway down the axis the 
bundles in the periphery increase toward the center, presenting the 
same condition as in Coix and Zea, again returning to the periphery 
and disappearing as they approach the radicle. The insertion of the 
scutellum-bondle is not as in Coix, Zea, and EucMama at some distance 
from the plumule but directly under it, where the plumule-sheath also 
branches off (fig. 6). The scutellum-bundle soon after leaving the axis 
divides, one branch traversing the lower, and the other the upper part 
of the scutellum, while these in turn have lateral branches (fig. 6). 
Aside from these bundles connected with the vascular system there are 
conducting vessels running irregularly through the scutellum, appar- 
ently nourishing organs for the plumule and radicle, as they can be 
traced to be directly connected through the epithelial layer with the 
other parts of the embryo (fig. 6). 

UucJilcena mexicana Schrad. (fig. 8, PI. II). — The structure of the 
embryo of JEuchkma is almost identical with that of Zea mays, except 
that it has no secondary radicles and the insertion of the scutellum- 
bundle is at some distance from the plumule. 

Tribe Andropogone^. 

The fruits of the tribe Andropogonew have an embryo which is usually 
about half the size of the fruit itself. As in the Maydece^ the scutelhim 
almost completely surrounds the remainder of the embryo. By com- 
paring the embryo of Andropogon (fig. 9, PI. II) with Zea (fig. 3, PI. 1) 
one notices a striking similarity. The scutellum-bundle is inserted on 



28 

tlie axis at some distance from the plumule, as in tlie majority of tlie 
Maydew. 

Andropogon saceharatiis (fig. 9, 10, A-0 PI. II). — The scutellum almost 
surrounds the plumule. The projection appearing in fig. 9 like an epi- 
blast is only a longitudinal section through one of the margins of the 
scutellum. The scutellum-bundle is inserted on the axis at some dis- 
tance from the plumule, while directly under the idumule two bundles 
branch off into the plumule-sheath. Fig. 10 A shows a section through 
the plumule with its plumule-sheath and bundles of the first true leaf, 
while fig. 10 B represeuts a section taken through the axis between the 
plumule aud the insertion of the scutellum bundle. Only one radicle 
is present with a large vessel in the center and five smaller ones 
around it in the central cylinder (fig. 10 C). There is a deep groove 
between the scutellum and the coleorhiza. 

Apluda cristata (figs. 11, 12, PL II). — The embryo of Apliida cristata 
resembles those of the Alaydece and Chloridece. There is no epiblast. 
The radicle appears as in fig. 12, with one large vessel jand six smaller 
ones in the central cylinder. . This arrangement continues through the 
axis until near the insertion of the scutellum, where vascular bundles 
appear. These continue through the lengthened node as far as the 
base of the iDlunmle, where they send off branches into the plumule- 
sheath. The ring around the radicle in fig. 12 represents a cross section 
through the coleorhiza. 

Tribe Zoysie^. 

The Zoysiem resemble on the one hand the Andropogonea'^ through 
Trachys, Anthephora (fig. 13 A-E, 1 PI. II), and Ferotis (fig. 15 A-D), 
and on the other hand Oryzece through Zoysia (fig. 11 A-D) and Nazia. 
Bruns, in a list of genera, represents Nazia without an epiblast, while 
in his figures he represents it with an epiblast, both in longitudinal and 
transverse sections. The scutellum in Anthephora and Ferotis is 
inserted at some distance from the plumule, while in Zoysia it is 
inserted directly under it. The radicle of Zoysia is also curved in a 
horizontal direction like Oryza. 

Tribe Tristegine^. 

Unfortunately no representatives of this tribe could be secured. 
Bruns, however, who has investigated the fruits of Beclera and Arnn- 
dinella^ found them to be without an epiblast, and similar to the 
Zoysieoi. 

Tribe Panice^. 

The general appearance of the fruits of the Fanicew is similar to ' 
those of Andropogoneoi, They are, with one exception, without an epi- 
blast, and have the scutellum-bundle inserted at some distance from 
the plumule. Olyra is the only genus which has an epiblast. It is 



29 

described and figured by Bruns, and differs in every respect from the 
other Fanicece. The scutellum is broader than, long, while the plumule 
is covered by a very large epiblast. A peculiarity mentioned by Bruns 
is that the radicle is hollowed out. Owing to the general appearance 
of the fruit and embryo, with its large epiblast and the insertion of the 
scutellum-bundle, also the fact that the flower is monoecious, would seem 
to indicate that it does not belong to the Fanicece. It might, perhaps, 
be placed with the Oryzece or form an intermediate tribe with Zoysia 
between the Fcmiceca and Oryzece. 

Fennisetum spicatum (figs. 16, 17, 18, PI. II). — The fruit of Fennisetum 
has a very large embryo. The scutellum surrounds the remainder of 
the embryo, although not to such an extent as in the Andropogonece 
and Mayclece. The projection opposite the scutellum in fig. 16 is not 
an epiblast, but a longitudinal section through the margin of the scu- 
tellum. A single large radicle is present, which consists of one large 
vessel in the center and six small ones surrounding it in the central 
cylinder (fig. 18). The ring around the radicle represents the coleorhiza 
with its attachment to the scutellum. Fig. 17 represents a cross section 
through the plumule, showing the scutellum with its bundle and the 
plumule-sheath with its two lateral bundles. Within is the first true 
leaf. The scutellum-bundle is inserted on the axis at some distance 
from the plumule (fig. 18). 

Ghcetocliloa onacrochceta (fig. 19, PI. III). — The embryo of this nut-like 
fruit resembles in the main other Fcmicece. The insertion of the 
scutellum-bundle is, however, somewhat closer to the plumule. A deep 
cleft or groove is present between the scutellum and coleorhiza. 

Faspalum puMflorum cjlabrum (figs. 20, 21, PI. III). — The embryo of 
Pcispalum resembles that of Fennisetum^ although much smaller. It 
possesses a large radicle, and its scutellum-bundle is inserted at some 
distance from the plumule. 

Tribe Oryze^. 

To this tribe belong, among others, the genera Romalocenclirus^ 
Zizania, and Oryza. Great variation occurs in the size and formation 
of the fruits. The embryo is usually small compared with the amount 
of endosperm, but in Zizania it attains a considerable size. All the 
genera belonging to this tribe have a well-marked epiblast. 

Zizania aquatica (figs. 22, 23 A-B, 24 A-T, PI. Ill) (see p. 21).— The 
fruit of Zizania is long and linear, with an epiblast which reaches three- 
quarters the length of the whole fruit. Pigs 23 A and B show the rela- 
tive size of embryo and endosperm; A through the plumule, and B 
through the axis or lengthened node. Figs. 24 A-T represent a series 
of sections through the embryo from the apex of the plumule-sheath 
to the main radicle. A and B show the two vascular bundles of the 
plumule- sheath, which at this point are united into one. At and D 
they have become sei^arated, while at E the plumule-sheath appears as 



30 

a complete ring, inclosing the upper part of the first leaf. The opening 
in the plumule-sheath on the side opposite to the scutellum now appears 
for a short distance as shown at G. At H, I, and J it is again closed, 
and within is seen the arrangement of the leaves of the plumule. K 
shows the first appearance of the epiblast, while at M it has increased 
in size. Within the plumule- sheath and first leaf one sees the axis 
with its bundles which belong to the remaining leaves of the plumule. 
Immediately below the i)lumule are three secondary radicles repre- 
sented in iS and O. The embryo for a considerable distance presents a 
form similar to that shown at P. The vascular system in the region 
of the secondary radicles i) resents a confused mass, but here it consists 
of two regular strands which course the lengthened node. As they 
approach the insertion of the scutellum the inner one becomes larger 
until it unites with the bundle of the scutellum. E shows the attach- 
ment of the epiblast to the axis, the division being marked by a dotted 
line, while T is a section through the main radicle surrounded by its 
coleorhiza. 

Homalocenchrus oryzoides (fig. -i8, PI. IV). — The fruits of Homalocen- 
cJirus, although much smaller and of a different form from that of 
Ziza7iia, yet in the main i^ossess the same structural characters of the 
embryo. 

Lygeiim spartimi (figs. 25, 26 A-E, PI. V^), — The embryo of Lygeum 
differs from the other genera of the Oryzew examined in having a very 
small epiblast. The insertion of the scutellum-bundle occurs directly 
beneath the plumule. Also at this point branches are sent off* into tbe 
plumule- sheath (fig. 26 B). The radicle is here lengthened out to a 
considerable extent. Lateral roots also arise from the node, as in fig. 
26 and D. Fig. 26 E shows a section through the main radicle, while 
26 shows parts of the secondary radicles and the base of the epiblast. 

Oryza sativa (fig. 27, PI. lY). — Compared with the amount of endo- 
sperm, Oryza has a very small embryo. The epiblast is large and 
broad at the base. As in Lygeum, the insertion of the scutellum is at 
the base of the plumule. The large radicle is directed obliquely 
outward. 

Tribe Piialaride^. 

Of the Phalaridece only Phalaris and AnthoxantJmm (fig. 29, PI. IT) 
were examined. These much resemble the Agrostidece, having a small 
epiblast and a straight radicle. The scutellum-bundle is inserted at 
the base of the plumule-sheath. 

Tribe Agrostide^. 

The Agrostidece may be characterized as fruits with small embryos, 
always with an epiblast, which, however, varies greatly in size. The 
scutellum-bundle is inserted on the axis at the base of the iDlumule. 
Here it branches to the right and left, running np into the x)himule- 



31 

slieatb. The short axis terminates in a single radicle. Among the 
peculiarities noticed in this tribe is the genus Stijya. Stipa ])ennata has 
a well-marked epiblast more than half the length of the plumule, while 
S. tenacissima (figs. 30 and 31, PI. lY) has a very small epiblast. In 
fig. 31 the opening of t)ie plumule-sheath is apparent. In )Sti])a ricliard- 
soni (figs. 3G and 37 A and B, PI. Y) the epiblast extends more than 
half the length of the plumule, and the radicle is directed obliquely 
outward. Although ;S'. viridula (figs. 32 and 33, PI. lY) has a very 
small fruit, yet its embryo has proportionately the largest epiblast. 

Eriocoma cuspidata (figs. 31 and 35, PI. lY). — The fruit of Eriocoma 
resembles that of Oryzopsis^ but has a very large epiblast which extends 
the whole length of the plumule. The scutellum differs from Oryzopsis 
in having a groove at its base. This character, together with the long, 
densely hairj^, flowering glumes, would warrant its being placed as a 
separate genus Eriocoma^ which is regarded as a subgenus by Hack el. 

Oryzopsis micraniha (figs. 38 A and B, PI. Y), Fhleimi pratense (fig. 
41, PI. Y), Cinna arundinacea (figs. 39 and 40, PI. Y), and BrachyeJy- 
triim erectum (fig. 43, PI. Y) all have a well-marked epiblast. The last 
named can easily be recognized by a long, pointed projection proceeding 
from the pericarj). This projection contains no starch, and its presence 
is remarkable from the fact that it is the only fruit in w^hich such a 
structure has been found. Ammophila arenaria (fig. 42, PI. Y) presents 
a peculiar appearance. Its cotyledonary sheath extends down to the 
ai^ex of the plumule. The scutellum also branches into three in the 
upper part. 

Tribe Avene^. 

The Avenece resemble the Eordece in the structure of fruits. The 
embrj'O is usually small compared with the amount of endosperm. 
Lateral roots occur in Avena. The scutellum-bundle is inserted at the 
base of the plumule and continues down into the axis in the form of a 
loop. 

Avena sativa (figs. 44, 45, 46 A-B, 47 A-G, 48, Pis. Y and YI).— Fig. 
47 A-G, Pi. Y, represents a series of transverse sections through the 
embryo from the plumule to the radicles. At A one sees the peculiar 
shape of the scutellum, with its vascular bundle, while withia is the 
l)lumule-sheath, with its bundles, inclosing the first true leaf. B repre- 
sents a section taken somewhat lower down in the plumule and shows 
the position of the second leaf directly opposed to the first. The scu- 
tellum-bundle branches at the base of the plumule, as may be seen at 
C, to form the bundles of the plumule-sheath. Part of the plumule- 
sheath is still present, while within is the axis with the first leaf and 
its bundles just beginning to differentiate. Figs. D, E, and F show 
the axis, and the epiblast which becomes larger toward the base. At 
E only one radicle is present while at F there are three. G shows the 
position of the four radicles. The main radicle is in the center with 
one on each side to the right and left, and a fourth smaller one in front. 



32 

A longitudinal section of this small radicle may be seen in fig. 48, 
PI. yi. The scutellum-bundle forms a loop in the axis as in fig. 48, a 
strand branching off from it forms the central bundle of the first true 
leaf. Fig. 45, PI. Y, represents a section facing the embrj-o. The main 
radicle with its two lateral radicles to the right and left are ail sur- 
rounded by a coleorhiza. Pigs. 44 and 46 A and B, PI. Y, represent 
longitudinal and transverse sections through the whole fruit showing 
the relative size of endosperm to embryo. 

Holcus lanatus (fig. 51, PI. YI.), Arrhenatherum eJathis (fig. 49), and 
Danthonia spicata (fig. 50) all have a small epiblast and a single termi-^ 
nal radicle with the scutellum-bundle inserted directly under the 
plumule. 

Tribe Chloride /E. 

The CMoridece, according to the characters of their embryos, are 
more closely allied to the Andropogoneoi than to the Avenece and FesUi- 
cecB, with which they are placed in Hackel's classification. The fruit varies 
considerably both in regard to its form and the structure of tlie embryo. 
There is a spherical nut-like fruit, as in Eleusine (fig. 52 A-D, PI. YI), 
with a well-marked epiblast, and a loag linear fruit with an embryo 
more than half the size of the fruit itself and without an epiblast, as in 
Spartina gracilis (fig. 53). The scntellum is inserted on the axis at 
some distance from the plumule. 

Eleusine coracana (fig. 52 A-D, PI. YI). — This peculiar nut-like fruit 
has an embryo with a very large epiblast. The radicle is in a hori- 
zontal direction, while a deei) groove is i)resent between the scutellum 
and coleorhiza. The insertion of the scutellum-bundle is close to the 
base of the plumule, while the axis between the plumule and radicle is 
very short. Fig. 52 A represents a longitudinal section through the 
embryo, while at B we see the plumule with the large epiblast pro- 
tecting it. 

Spartina gracilis figs. 55, 54 A-0, PI. YI). — In contrast to Eleusine 
it has a long linear fruit with an embryo reaching almost its whole 
length. The general appearance of the embryo reminds one of Zizania 
acjuatica, as the insertion of the scutellum is a considerable distance 
from the plamule-sheath. One single vascular strand courses the length- 
ened node until it sends off a branch to the scutellum, and then con- 
tinues down into the very small radicle. Fig. 54 A, B, show sections 
through the radicle, lengthened node, and i)lumule, respectively. It is a 
noteworthy fact that this is the only genus of the Chloridece examined 
which does not have an epiblast. 

Astrehla pectinata (fig. 55, PI. YI). — The embryo of AstreMa is very 
large, with a very small epiblast. A deep groove is present between 
the scutellum and the coleorhiza. The scutellum-bundle is inserted on 
the axis at some distance from the plumule. The axis terminates in 
a single radicle, which i3reserves its root structure until just before it 
reaches the insertion of the scutellum, where vascular bundles appear. 



33 

Bechnannia erucceformis (fig. 60, PI. YI), Bulbilis dactyloides (figs. 58 
aud 59, PI. Vl)j and Leptochloa hnbricata (fig. 50, PI. VI) liave about 
tlie same characteristics. 

Tribe Festuce^. 

The embryo of the Festucew is usually small. There is, according 
to Bruns, great variation in the presence and absence of an epiblast 
in this tribe. 

Vniola latifoUa (fig. 61, PI. VII). — A broad epiblast reaches about 
half the length of the plumule. The scutellum-bundle is inserted on 
the axis at some distance from the plumule, while the single radicle is 
turned obliquely outwards. 

Desmazeria sicula (fig. 63, PI. VII), Ci/nosiirus cristatus (fig. 64), and 
Panicularia aquatica (fig. 62, PI. VII) all have the epiblast well marked. 
The scutellum-bundle differs from that of TJniola in being inserted 
directly at the base of the plumule. The axis terminates in a single 
radicle. 

Tribe Horded. 

The tribe Hordece may be characterized as having large fruits. The 
embryo usually has several radicles and a lateral bud in the axil of the 
plumule-sheath. A transition seems to take iDlace between those with- 
out an epiblast, as in Hordeum (fig. 65, PI. VII), and those with a dis- 
tinctly formed epiblast as in Triticiim (fig. 69, PI. VII). 

Eordeum viilgare (fig. 65, 66 A-H, PI. VII). The fruit of Hordeum 
vulgare has many i)eculiarities not found in other grasses. There are 
two, and in some parts three, layers of gluten cells, while in nearly all 
grass fruits there is only one. This embryo often has, besides its main 
radicle, eight secondary ones, three on each side of the scutellum and 
two in front. In the axil of the plumule-sheath next the scutellum 
there is a large lateral bud (see p. 20). By examining figs. A-F it will 
be seen that the scutellum-bundle is composed of two strands which 
unite just before their insertion on the axis. The scutellum is inserted 
on the axis at the base of the i^lumule, a secondary radicle also emerg- 
ing from it at this point, thus making the axis very short. At fig. 65 
the bundles may be seen which belong to the first and second leaves 
and the vegetation point. Those of the plumule-sheath not being in 
the same plane are not represented. A transverse section through the 
upper part of the plumule (fig. 66) shows the opening in the sheath 
opposite to the scutellum and the two bundles situated laterally. 
Within is the upper part of the first true leaf. The scutellum shows 
a peculiar groove on its convex side next to the endosi)erm (fig. 66^ A, B). 

B shows a similar condition a little lower down through the plumule. 
At G and D the position of the first leaf opposite to the x)lumule- sheath, 
the second opposite the first, and the third opposite the second, accord- 
ing to the true distichous arrangement of all grass leaves may be noted. 
20946— :N^o. 19 3 



34 

E shows a section taken at the base of the i)lumule with the bundles in 
the axis which belong to the leaves of the plumule, also the two bun- 
dles of the disappearing plumule-sheath. At F the scutellum bundles 
are inserted on the axis. On the opposite side are two secondary rad- 
icles in the center of the bundles of the axis, while to the right and left 
appear the origin of the bundles of the plumule-sheath. At C the 
scutellum-bundles are no longer present, while three secondary radicles 
emerge from the axis. Four of the secondary radicles may be seen at 
H with the axis continuing down to form the main radicle. These rad- 
icles are all provided with a root-cap and surrounded by the coleorhiza. 
Although no epiblast is found here yet there is a slight prominence 
which might indicate its abortion. 

Secale montanum (figs. 67, ^% A and B, PI. VII). — The structure of 
the fruit of Secale resembles that of Hordeum vulgar e. There is how- 
ever only one secondary radicle. Not even a trace of an epiblast can 
be seen. The coleorhiza surrounds both radicles, forming a deep groove 
between them. At the base of the plumule-sheath next to the scutel- 
lum there is a lateral bud. The scutellum-bundle consists of a single 
strand, which is inserted on the axis almost directly at the base of the 
plumule. At this point branches are sent off into the plumule-sheath. 
The bundles in the axis belong to the leaves of the plumule while the 
axis continues down into the main radicle, a branch beiug sent off to 
the secondary radicle. Fig. Q^ B represents a transverse section 
through the upper part of the i)lumule and A through the main and 
secondary radicles. 

Elymus virginicus (figs. 72 and 73, PI. YIII). — The fruit of Elymus 
has a very small embryo at the base of a loug fruit. Although the 
epiblast is not ijresent yet there is a slight elevation which might be 
regarded as a remnant of it. The scutellum bundle consists of a single 
strand which curves around to the base of the plumule where it 
divides into three branches, two of them going into the plumule-sheath 
and the other continuing down into the axis and single radicle. A 
lateral bud is present in the axil of the plumule-sheath. Fig. 73 rep- 
resents a transverse section through the upper part of the plumule. 

Lolium rigidum (figs. 70, 71 A-G, PI. YIII). — The embryo of Lolium 
resembles Secale montanum with only one large radicle. A lateral bud 
is present in the axil of the plumule-sheath. 

Triticum cestivum (fig. 69, PI. YII). — The fruit of Triticum cestivum 
has been so frequently described by previous writers that it is not 
necessary to treat it at length here. An excellent treatise by Bessey is 
to be found in Bull. 32 of the JS^ebraska Agr. Exp. Station, 1894. Its 
embryo has a small epiblast, a main radicle, and two secondary ones 
situated in front to the right and left. There is a prominent lateral 
bud in the axil of the plumule-sheath. In all other respects it resembles 
the tribe Hordew. 



35 

Tribe Bambuse^. 

A small plant of Arundinaria falcata bloomed in the Cornell nursery 
during the summer of 1898. About a dozen fruits were secured and 
sections of the embryo made. 

The fruit is oval and is covered by a pericari3, which easily separates 
from the endosperm and embryo. The embryo is small, with its scutel- 
lum almost completely surrounding the plumule (fig. 74, PI. YIII). The 
vascular bundle traversing it is branched in all directions, as shown in 
any of the transverse sections (fig. 76 A-J,*P1. VIII). 

The plumule-sheath differs from all other fruits of the Graminew 
investigated in having five vascular bundles instead of two. At its 
apex there is a well-marked slit or opening and only two vascular 
bunches (fig. 76 0). Figs. 76 D, E, F show the position of the five vas- 
cular bundles inclined toward the exterior side of the embryo. 

The leaves have seven vascular bundles and are arranged as in all 
grass embryos (fig. 76 E). The epiblast is large and broad, but does not 
extend far up on the plumule. Toward the base it is rectangular in 
cross section (fig. 76 G, H). The axis terminates in one large radicle 
(fig. 76 K). 

RELATIONSHIP AND SYSTEMATIC CONNECTION OP THE TRIBES. 

Botanists disagree very generally as to which are the most primitive 
tribes of the grasses. The three great authorities on the subject are 
Hackel,^ Bentham,^ and Warming.^ Their classifications are as follows : 

bentham's classification. 



A. Panicacea'. 

Tribe I. Paniceae. 
II. Maydese. 

III. Oryzese. 

IV. Tristeginete . 
V. Zoysiese. 

VI. Andropogonete. 



B. Poaceo". 

Tribe VII. Phalaridete. 

VIII. Agrostideae. 

IX. Isachnese. 

X. Aveneoe. 

XI. CWoridege. 

XII. Festucese. 

XIII. Hordes. 

XIV. BambusesB 



hackel's classification. 



A. Panicacefv. 

Tribe I. Maydeae. 

II. Andropogoneae. 

III. Zoysiese. 

IV. Tristegineae. 
V. Paniceae. 

VI. Oryzeae. 



j B. Poacece. 

Tribe VII. Pbalarideae. 

VIII. Agrostideae. 

IX. Aveneae. 

X, Chlorideae. 

XI. Festucete. 

XII. Hoidea?. 

XIII. Bambuseae. 



^Hackel, E. Echte Graeser. Engler and Prautl, Pflanzenfamilien, 2^ : 2. 
Eng. trans, by Scribner and Southworth, 1890. 

^Beutham, Geo. ^'Notes on Gramineae," Jour, of the Linn. Soc, 19 : 14-134, 1881-82. 
^Warming, E., and Potter, C, Systematic Botany. 



36 



warming's classification. 



Tribe 1. Bambusese. 

II. Oryzeae. 

III. Maydese. 

IV. Aiidroj)ogone{ei 
V. Festucese. 

VI. AvenesB. 



Tribe VII. AgrostidetB. 
VIII. Phalaridese. 
IX. Cbloridese. 
X. PanicejB. 
XI. HordeaB. 



It will be noticed that Hackel's arrangement is in the main similar 
to that of Benlham, while Warming's varies, omitting the tribes Zoy- 
stem and Tristeginew. Bentham, on the one hand, regards the tribes 
FaniceWj Maydecc^ and Oryzew, while on the other, Hackel places the 
3Iaydecej Andropogonece, and Zoysiece as the most primitive of the 
grasses. Warming^ however, presents an entirely different view, and 
regards the Bamhusece and Oryzece as the most primitive. 

This great difference of opinion is probably due to the fact that the 
grasses have been largely studied from the basis of only a single char- 
acter. Hackel ^ claims to have discovered the magic spell by which all 
difficulties must come to an end in regard to the arrangement of the 
genera of the Andropogonew, but it is to be doubted whether the same 
can be said of his arrangement of the tribes. The Andropogonece 
together with the Maydew, Panicew^ TristegineWj and Zoysiece without 
doubt represent a very natural group of the Graminece, but it is a ques- 
tion whether they are the most primitive. Tf one studies the Andropo- 
gonece from the standpoint of their resemblance to other Monocotyle- 
dons one is unable to find the slightest trace of such resemblances iu 
any of the genera, while among the Bamhusece and Oryzece there are 
many similarities. 

The Bamhusece are characterized as large, often tree-like, grasses, 
with woody, rarely herbaceous culms. The leaves are broad, some- 
times compound and usually xietioled. There are from three to six, or 
many, stamens while the prevailing number in the other Graminece is 
two or three. Usually three remarkably large lodicules ^ are present 
on the rhachilla. There is great variation in the structure and iu the 
form of the fruit. Both Munro^ and Hackel^ use fruit characters to 
divide the different genera into sections. They may be classified as 
the berry -bearing and the true bamboos, the latter with linear or 
oblong-linear fruits, like those of Avena and Tritlcum, with a distinct 
furrow down one side and the scutellum visible below. 

In the berry-bearing bamboos the caryopsis appears to be contained 
in an envelope somewhat analogous to the sac or perigynium which 
incloses the seed of Carex, In Melocanna hamhusoides this covering 

1 Hackel, E., Audropogoneje. De Candolle's MonograpMe Pbaner. 

2Rowlee, W. W. The Morphological Significance of the Lodicules of Grasses. 
Bot. Gaz. 25 : 199-203. 1898. 

^Munro, Memoir on Bambusese. Trans, of the Linn. Soc. xxvi: 

^Hackel, R., Echte Gr^eser. Engler audPrantl, Pflanzenfamilien, ii^: p. 92. Eng. 
trans, by Scribner and Southworth. 



37 

becomes very fleshy and the fruit attains the size of a large pear. 
Schizostachyum acutiflorum has very curious bundles of hairs on the 
scutellum, and the pericarp of the oblong fruit is quite loose and rugose. 
Some of the genera of the section Triglossece approach very closely in 
the structure of the spikelet the tribe Panicece. 

The Oryzece may be compared with the Bamhusece. In regard to their 
leaves there is a great variety of forms, from broad, ovate, petiolate 
leaves in Fharus, to long, linear ones in Zizania, and short, narrow 
lejaves rounded at the apex in Hydrocliloa. There is also great varia- 
tion in the inflorescence. In some of the genera a number of bracts are 
arranged spirally around the main axis, while in others the inflores- 
cence is inclosed in a spathiform envelope. The normal number of 
stamens is six, although they vary from one to eight. The ])istil 
usually branches into two plumose stigmas, with occasionally a three- 
branched style, as in Pharus. The lodicules vary from 2 to 3. There 
are long, linear fruits, as in Pharus, and oblong-linear fruits, as in Oryza. 
The Oryzece therefore resemble the Bamhusece in the following respects : 
(1) They show great variation in the structure of their fruit and spike- 
let. (2) Both have remarkably large epiblasts. (3) Some genera have 
the same number of lodicules. (4) Pharus has a style with three stig- 
mas. (5) Many of the genera have broad petiolate leaves and transi- 
tions between these to linear ones. (6) They have to a great extent the 
same geographical distribution, the larger number of the genera being 
indigenous to tropical America. It would appear tlierefore that the 
Oryzew are closely related to the Bamhusece, and that together they 
represent the most primitive of the grasses, thus bringing them nearer 
to the other Monocotyledons (e. g., Palmcicece). So far as it has been 
observed there appears to be no similarity between the Bamhusew and 
Hordece, although they are looked upon by both Bentham and Hackel 
as being closely allied. 

The Zoysiece, Tristegmece, Andropogonece, Maydece, and Panicece, both 
according to the characters of the fruit and those of the inflorescence, 
according to Hackel's classification, form another natural group, joined 
to the Oryzece through the Zoysiece and Tristeginece. The Chloridece, 
although regarded by both Hackel and Warming as being removed 
some distance from the Andropogonece, are like them in their fruit 
characters. 

The remaining tribes, Phalaridece, Agrostidece, Avenece, Festucece, and 
Ilordece, from their fruit characters, form another group in the order 
named, which corresponds with the classification given by Hackel. 



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EXPLANATION OF PLATES. 



Plate I. 



Fig. 1. Coix Iachrym(e-johi, long, sec; (x 7). 

2 A-D. Coix lachrymce-jobi, cross sec. of embryo; (x 9). 

3. Zea mays, long. sec. of embryo; (x 5). 

4 A-F. Zea mays, cross sec. of embryo; (x 14). 

5. THpsacum dactyloides, long. sec. facing embryo; (x 8). 

6. THpsacum dactyloides, long, eec; (x 8j. 

7 A and B. Tripsacum dactyloides, cross sec. ; (x 8). 

Plate II. 

8. Uuehkena mexicana, long. sec. of embryo; (x 23). 

9. Andropogon saccharatus, long. sec. ; (x 19), 

30 A-C. Androjyogon saccharatus, cross aec, (x 34). 

11. Jpluda eristata, long, sec; (x 12). 

12. Apluda eristata, cross sec. ; (x 30). 

13 A-E. Anthephora elegans, long, and cross sec; (x 17). 

14 A-D. Zoysia-pungens, Jong and cross sec ; (x 12). 

15 A-D. Perotis latifoUa, long, and cross sec ; (x 17). 

16. Pennisetum spicatum, long, sec; (x 12). 

17. Pennisetum spicatum, cross sec. ; (x 16). 

18. Pennisetum spicatum, cross sec. ; (x 28). 

Plate III. 

19. Chcetocldoa macrocha^ta, long, sec; (x 13). 

20. Paspalum xniMfiorum glahrum, long, sec; (x20). 

21. Paspalum puMflorum gldbrum, cross sec ; (x 12). 

22. Zizania aquatica, long, sec; (x 5). 

23 A and B. Zizania aquatica, cross sec; (x 10). 

24 A-T. Zizania aquatica, cross sec of embryo; (x 6). 

Plate IV. 

2.5. Lygeum spartum, long, sec; (x 6.5). 
26 A-E. Lygeum spartiim, cross sec; (x 18). 

27. Oryza sativa, long. sec. ; (x 7). 

28. Homalocen chr us or yzoiCss, long, sec; (xl4). 

29. AntJioxanthum odoratum, long. sec. ; (x 23). 

30. Stipa tenacissima, long, sec; (x 20). 

31. Stipa tenacissima, cross sec; (x24). 

32. Stipa viridida, long, sec; (x 14). 

33. Stijni viridula, cross sec; (x 42). 

34. Eriocoma cuspidata, long. sec. ; (x 17). 

35. Eriocoma cuspidata, cross sec; (x 43). 

43 



44 

Plate Y. 

Fig. 36. Stipa ricliardsoni, long, sec; (x 17). 

37 A and B. Stiim ricliardsoni, cross sec. ; (x 24). 

38 A. Oryzopsis micranthaj long, and cross sec. ; (x 14). 
38 B. Oryzopsis micrantha, long, and cross sec. ; (x 29). 

39. Cinna arundinacea, long, sec; (x 10). 

40. Cinna arundinacea, GTo&QiiQC.] (x50). 

41. Plileum pratense, long. &ec.) (xl8). 

42. Ammophila arenaria, long. sec. ; (x 20). 

43. Bracliyelyirum erectum, long, sec; (x 6). 

44. Arena sativa, long. sec. ; (x 5). 

45. Arena sativa, long, sec facing embryo; (x 6). 

46 A and B. Arena sativa^ cross sec. ; (x 10). 

47 A-G. Arena sativa, cross sec. of embryo; (x 13). 

Plate YI. 

48. Avena sativa, long. sec. of embryo; (x 13). 

49. Arrhenaiheritm elatius, long, sec; (x 11). 

50. Dantlionia spicata, long. sec. ; (x 17). 

51. Holcus lanatus, long, sec ; (x 20). 

52 A-D. Eleusine coracana, long, and cross sec. ; (x 13). 

53. Spartina gj-aciJis, long. sec. ; (x 9). 

54 A-C. Spartina gracilis, cross sec; (x 16). 

55. AstrehJapectinata, long. s,Qc.', (x20). 

56. Leptochloa imbricata, long. sec. ; (x 27). 

57. Cynodon daetylon, long. sec. ; (x 31). 

58. Bulhilis dactyloides, long, sec ; (x 18). 

59. Bulbilis dactyloides, cross nee.', (x 18). 

60. Beckmannia eruccvformis, long. sec. ; (x 26). 

Plate YTI. 

61. TJniola latifolia, long. sec. ; (x 10). 

62. Panicularia aquatica, long, sec; (x 17). 

63. Desmazeria sicula, long, sec; (x 17). 

64. Cynosurus cristatns, long. sec. ; (x 16). 

65. Hordeum vulgare, long. sec. of embryo; (x 9). 

66 A-H. Hordeum vulgare, cross sec. of embryo; (x 18). 

67. Secale montatnun, long. sec. ; (xl5). 

68 A and B. Secale montanum, cross, sec ; (x 14). 

69. Triticum (estivum, long. sec. of embryo; (x 13). 

Plate YIII. 

70. Lolium rigidum, long, sec; (x 16). 

71 A-C. Lolium rigiduin, cross sec; (x 24). 

72. Elymus virginicus, long. sec. ; (x 11). 

73. Elymus virginicus, cross sec. ; (x 32). 

74. Arundinaria falcata, long. sec. of embryo parallel to scutellum; (x 19). 

75. Arundinaria falcata, long. sec. of embryo; (x 16). 

76 A-K. Arundinaria falcata, cross sec of embryo; (x 29). 



Bui. 19, Div. of Agrostology. 



Plate I, 




Structure of the Caryopsis of Grasses. 



Bui. 19, Div of Agrostology. 



Plate II. 




Structure of the Caryopsis of Grasses. 



B\j\. 19, Dhv of Ag'ostology. 



Plate II 



24- A 



24 B 




24 D 



24 R 



24 S 



24T 




24C\^^/^ 



Structure of the Caryopsis of Grasses. 



Bui. 19, Div. of Agrosto'ogy. 



Plate IV. 




Structure of the Caryopsis of Grasses. 



Eu!. 19. Div. of Agrostology. 



Plate V. 




Structure of the Caryopsis of Grasses. 



Bui 19, Div. of Agrostology. 



Plate VI. 




Structure of the Caryopsis of Grasses. 



Bui. 19, Div. of Agrostology. 



Plate VII. 




Structure of the Caryopsis of Grasses. 



5ul. 19. Div. of Agrostology. 



Plate VIII. 




Structure of the Caryopsis of Grasses. 



I 



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